The arrival of Microsoft Exchange Server 2003 (ES2K3) is a significant event in the history of this product. First, it brings to a close the second era of the codebase. Released back in 1996 on the NT 4 wave, ES4 (there was no 1, 2 or 3) brought enterprise-level email, contact management, diary management and so forth to the Windows Server platform in a new and comprehensive BackOffice application. The only comparable rival was Lotus Notes, and even then there were more differences than similarities between these two goliaths.

The first generation of Exchange Server lasted from ES4 to ES5 and thence to ES5.5, by which point it had also found a home within the Small Business Server 4.5 platform. By the final service pack of ES5.5, it had grown into a robust and capable platform that still does good work today for many companies. Note the phrase 'by the final service pack' -- with ES, Microsoft has never shied away from adding useful new functionality in the service packs. Hence, service pack releases to Exchange Server have always been eagerly awaited to see what new tweaks were introduced.

With the arrival of ES2K, the second generation of the Exchange Server story emerged. This release required Windows 2000 Server and its new Active Directory infrastructure. For many, this was a leap too big to contemplate, which is why they're still on NT 4 and ES5.5. For those who made the move, there was a whole new raft of capabilities. Although the underlying storage engines weren't changed, there were improvements for the larger customers. Manageability and ease of use were considerably bettered too and, naturally, there were substantial improvements to the Outlook client as well. However, you had to understand Active Directory to make it work.

And now, with the arrival of ES2K3, the second wave is coming to an end. In all truthfulness, ES2K3 can be seen as a big service pack to the fundamental ES2K platform. Everywhere you look, there are improvements - manageability, performance, security, scalability and so on. But the major building blocks are the same. It will be the next big release of Exchange Server, probably ES2K6, before we see the beginning of the third wave of Exchange Server development.
To predict the changes this will bring, you need to under

stand that this is almost certainly the last large monolithic two-tier BackOffice application Microsoft will ever ship. Compared with the programming paradigms emerging from Redmond in Visual Studio, its XML work and the push to a new set of unified middle-tier application servers and services, ES2K3 is a big lumbering monster. The third generation will move Exchange Server into this new world order. So the storage will unify onto the forthcoming Yukon SQL Server engine and the WinFS underpinnings. The little-used and almost invisible Exchange Server Event Handling Engine will be replaced by Jupiter middleware components. And the whole thing will be rewritten in Common Runtime Language components. It's a major step to look forward to. But, in the meantime, we have ES2K3 and it's time to consider whether it's a good product, whether you should move to it and whether it's enough.

New features

Let's look at some of the new features in ES2K3. First, you should understand that this is probably the last chance there is for ES5.5 users to move forward in a controlled fashion. I have serious doubts as to whether Microsoft will support ES5.5 to ES2K6 in one step -- you might have to do a dump right down to PST files to get data transferred. Plus, because primary support on ES5.5 is about to cease, you should be giving serious considerations to your upgrade routes from that platform now.

ES2K3 inherits new capabilities and features from Windows Server 2003 (WS2K3) too, of course, so for a proper understanding of the full ES2K3 product you have to be running on WS2K3 as well. This isn't an onerous requirement, providing you remember the matrix of what runs on what. You can run any ES2K/2K3 on any Windows 2000/2003 combination with one exception - you can't run ES2K on W2K3. So the upgrade route is clear: start with ES2K on W2K, move to ES2K3 on W2K, and then move to ES2K3 on WS2K3.

Since you inherit the underlying capabilities of WS2K3, the clustering support is much better in ES2K3 compared to previous versions in that you can have up to eight machines in a cluster. However, the underlying limitations of mailboxes per store and so forth are still in place, so an Active/Active cluster solution has its limitations. But you can build better and more resilient solutions than before. ES2K3 also benefits from the snapshot file system capabilities of WS2K3. So if you're using a SAN (Storage Area Network), for example, you can break the mirror on the SAN and back up one half in real-time while the other part keeps running. Support for SAN and NAS (Network Attached Storage) is much better in WS2K3/ES2K3 than in previous versions, so you should be looking to these versions if you want to deploy a large SAN.

If you have a large multiserver implementation of Exchange Server, you'll know all about front-end/back-end server deployments, where you split the capabilities of Exchange Server into two halves and run them on different servers. In this environment, a good change is the removal of the requirement for Enterprise Server versions of ES2K3 as front-end servers to back-end Enterprise Server ES2K3s, which will be a significant licensing cost reduction for large sites.

Now let's look at the more user-oriented features that ES2K3 brings to the table. At this point, we need to assume you have Outlook 2003 installed as well, because the new online/offline capabilities of that pair are only available when you run both pieces. In a nutshell, you can run Outlook in a local cache mode whereby it keeps the data locally to the machine, yet pulls and pushes through the back-end ES2K3 server too. Connecting through port 80 is another feature of this combination and means you can actively synchronise over the Internet without needing to resort to Virtual Private Networks or the equivalent.

OWA (Outlook Web Access) has always been a killer feature of Exchange Server -- being able to read your mail, contacts and calendaring from anywhere just by using a browser is a powerful capability. With ES2K3, it has been dramatically improved. If you have a good enough browser, such as Internet Explorer 6, you get a rich desktop client running in the Web browser that's almost feature-for-feature compatible with the full native Outlook client. You can right click on things, drag and drop them and do all that sort of rich interaction. This is an astonishing and amazing piece of Web-development work and sets the benchmark for such programming. If you work on a lesser browser, the experience is obviously scaled back a little, but it's still light years ahead of the capabilities in previous versions of ES.

As a child of OWA, OMA (Outlook Mobile Access) is a new feature. OMA is a super-lightweight version of OWA aimed at the simple Web browsers found in PDAs and phones. You get full access to your inbox, including contacts and so forth, and it does so in a lightweight data way that doesn't chew up lots of bandwidth, unlike OWA which is traffic heavy. If you have a Pocket PC 2003 device or one of the forthcoming 2003 Windows Smartphones, you can even do a full ActiveSync synchronisation in real-time while away from the office. This is a significant step forward and has been enabled by building in technology that was previously available in the Mobile Information Server add-on to ES2K.

Some of the core message filtering has been improved too. Microsoft has put in place a full anti-spa